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A116896
Numbers k such that k! + k!! + 1 is prime, where k!! denotes double factorial (A001147).
1
0, 1, 2, 6, 42, 604, 1976, 5126
OFFSET
1,3
COMMENTS
1976! + 1976!! + 1 is a 5657-digit prime. Next term is greater than 4000.
EXAMPLE
6! + 6!! + 1 = 769, which is prime.
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Giovanni Resta, Mar 04 2006
EXTENSIONS
5126 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008
STATUS
approved